The invention relates to a cross cutting or cross severing device for a winding machine having at least one carrier roll, preferably two carrier rolls, to wind winding material, particularly paper or the like, in the form of a web, having a cross cutting or cross severing means in order to cut or sever a web after completion of a roll and having a clamping device in order to securely clamp the web edge formed by the cross cutting.
The cross cutting means features may border recesses which stand back behind the cutting edge, in which the clamping means of a clamping device can grasp. A cross cutting device of this type is known from DE-B-29 30 474. In order to start a cross cutting process with this known cross cutting device, first a holding strip or bar is pushed through a clearance gap between two carrier rolls. The holding strip or bar is located on the leading end in the running direction of a support in the form of a shell-shaped segment, and, after reaching its working position, can be pressed against the surface of a carrier roll around which a web is wrapped, with the aid of a pressurized drive having rounded finger elements. An arriving web is thus pressed in a clamping manner against a wrapped carrier roll in front of the cross cutting location in the web running direction. In order to later sever the web, a perforating strip extending approximately parallel to the axis of the carrier roll is swung counter to the rotating direction of the wrapped carrier roll into the cross cutting position. Here, the cross cutting blade pushes between the surface of the roll and the web to be cut and encounters the web to be cut through at a certain radial clearance from the surface of the carrier roll, that is from below. Here, the cross cutting force works counter to the holding force of the finger-shaped holding means. Provided that the cross cutting blades are sufficiently sharp and the material properties of the web to be severed are suitable, the web to be severed will be perforated near the clamping location determined by the clamping means. The cross cutting blade then further travels a short distance in its original running direction until the border recesses provided in the cross cutting blade and the finger-shaped clamping means mesh with each other. The cutting region of the cross cutting blade then is located above the web which has been crosscut, i.e., radially outside with respect to the carrier roll around which the web is wrapped. In this position, the blade-holding beam carrying the cross cutting blade is swung as a unit in such a manner that a border zone arching slightly outward near the blade edge will be pressed against the border zone of a web edge formed by means of the cutting process, such that this web edge will be clamped between the underside of the blade and the wrapped carrier roll. The holding means with clamping fingers then is swung back and drawn back though the clearance gap between the two carrier rolls, while the web edge formed by the cross cutting remains securely clamped by means of the cross cutting blade.
First, this known cross cutting device is costly and is provided with four driving means. Next, the combination of a clamping means and cross cutting blades working counter to the clamping means leads to a satisfactory result only if the cross cutting blade is sufficiently sharp and the quality of the web to be wound and crosscut is suitable for this type of perforating process. For example, when the web to be wound and to be cut crosswise is of a material reinforced in the web running direction, the danger exists that under the effect of the clamping fingers and cross cutting blade working counter to the web, the web will not only be perforated in a transverse direction but that it will also tear in a longitudinal direction at the lateral edges of the fingers. This results in a web being pressed down against the wrapped carrier roll in the region of the clamping means and continuing to be lifted in the region of the intermediate cross cutting zones of the wrapped carrier roll. If this occurs, it is no longer possible to move the cross cutting blade across the cross cutting location with the requisite certainty and later to press the edge zone of the web close to the cross cutting location down onto the carrier roll. Since the drives for the clamping means and cross cutting blade are independent of each other, it furthermore is difficult to coordinate the two components working interactively, i.e., clamping fingers and cross cutting blade, in such a manner that a mutual clamping position is achieved in which the clamping fingers and cross cutting blade are conducted counter to each other just far enough that they mesh with each other exactly.
Starting from here, the invention solves the problem of achieving and increased certainty of operation and simpler construction for a cross cutting device for the same generic class having a clamping device. This is solved in accordance with the invention by means of the fact that for a cross cutting device of the same generic class, the cross cutting means can be conducted in a manner known per se by a support beam through a clearance gap between two carrier rolls or, alternatively, close to the periphery of said first carrier roll into a cross cutting position located at or close to the surface of the carrier roll around which the web is wrapped, and comprising means to press the support beam and/or the cross cutting means by a finished roll of said winding material against the wrapped carrier roll, for the purpose of tightening and cutting the web, by means of the finished wrapped roll, and thatxe2x80x94eventuallyxe2x80x94a second clamping device can be conducted into its clamping position counter to the web running direction and there, overlapping the arriving web edge of the next roll to be wound, securely clamps it independently of the cross cutting means, and the cross cutting means can be conducted back through the clearance gap of the carrier rolls to its home position, and the eventual second clamping means, after a new winding core has been loaded, can be detached from the web edge and the clamping means can be conducted back in the web running direction.
The invention achieves a cross cutting of the web simply, due to the force of the weight of a finished wound roll in such a manner that the wound roll immobilizes the cross cutting means, which may act like a clamping means only, in a position which can be precisely determined beforehand, and the cross cutting process is carried out by tightening the web end along a straight line by moving the wound roll away from the first carrier roll, whereby the web becomes tightened longitudinally and breaks. It will be appreciated that the front end or edge of the support beam will clamp the arriving web end close to the intended cross cutting line very uniformly along an elongated straight line in cross machine direction. Even if the cross cutting means is of a non-sharp type or has lost its sharpness and/or the material of the web to be cut crosswise has a tendency to tear longitudinally, this type of cross cutting works safely. The cross cutting means immobilizes the web to be cut crosswise over the major length of the cross cutting line, thus tightening the web to be cut crosswise sufficiently along the cross cutting line to avoid a longitudinal tearing of the web, for instance at the edges of eventually provided recesses of the cross cutting means, or other cross cutting defects.
A cross cutting device, according to a first embodiment of this invention, for which a cross cutting blade can be conducted by a blade-holding beam through a clearance gap between two carrier rolls into the cutting position, and the blade-holding beam, for the purpose of tightening and cutting the web, can be pressed against the wrapped carrier roll by means of a finished wound roll is known per se from EP-A1-0 640 544, which is incorporated by reference herewith. However, this known cross cutting blade does not feature any border recesses and, in addition, the border zone of an arriving web edge, i.e., the start of the web for the next winding process, is pressed against the wrapped carrier roll only by means of the blade-holding beam and no other clamping means being used. When a new winding core is loaded, the known cross cutting blade therefore must be conducted back through the clearance gap between the two carrier rolls, and the arriving web must be held against the wrapped carrier roll by a different means, such as a vacuum, until the next winding core has been loaded and the next winding process has begun.
Unlike the cross cutting device known from DE-B1-29 30 474 mentioned here before the arriving web edge is, in accordance with the invention, held closely to the wrapped carrier roll by the support beam of the cross cutting means after the cross cutting process close to the cross cutting line on practically the entire length of the cross cutting line, preferably until the clamping means of a clamping device, coming from a direction counter to the general web running direction, has overlapped the crosscut web edge and has securely clamped the border zone of the arriving web edge close to the cross cutting means. This guarantees a secure function of this additional clamping device and avoids a case where the clamping means finds itself between the carrier roll surface and the web edge, where it would become ineffective.
An arrangement in accordance with the invention makes sure that the cross cutting means and its support beam, in comparison to other known cross cutting devices (JP-A-60-23 23 58), can be of a comparatively stable design and can be employed over a correspondingly long time, practically free of maintenance and with a secure function. Web material that requires a greater force to be crosscut is also capable of being crosscut without trouble.
While the comparatively stable cross cutting means and its support beam can be conducted back through the clearance gap between the two carrier rolls after the cross cutting process and after the new clamping means has overlapped the arriving web edge, only the comparatively small-dimensioned clamping device remains close to the cross cutting line, which does not hinder the consequent loading of a winding core or cores into the bed between the two carrier rolls for the next winding process. In particular, a winding core or cores can be loaded in a position which is extremely close to the cross cutting line, such that the new web start is located very close to the line of contact between the web and the new winding core or cores. The comparatively lightweight construction of the clamping device permits a rapid drawing back of the clamping device to its home position after a new winding core or cores has/have been loaded.
The cross cutting device according to the present invention can be practiced in various embodiments:
For instance, as a first embodiment, the cross cutting means can comprise a cross cutting blade which is fixed on the front edge of the support beam, such as known per se in the art. The cross cutting blade is more or less sharp and acts in a way that the web will tear off immediately at the cutting edge of the cross cutting blade as soon as the tensioned web touches said cutting edge under a sufficient angle. This happens when the wound roll is displaced from the wrapped carrier roll onto the cross cutting beam, for instance by lowering the non-wrapped (second) carrier roll. By this displacement of part of the weight of the wound roll from the wrapped carrier roll to the support beam, the front zone of the support beam, when seen in the web-running direction, abuts against the web close to the cross cutting position and further against the wrapped carrier roll.
According to another embodiment, the web is first perforated along the line at which the cross cutting has to take place.
Although the web may be perforated on a place of the web prior to that place on the web contacting the first carrier roll, the preferred embodiment is to perforate at a location already in contact with the first carrier roll. This location is preferred because the sheet is held flat to avoid stress concentration that might cause the sheet to tear prematurely. Before the carrier roll, additional equipment would be required to insure this. Another advantage of the preferred embodiment is that the angle of wrap between the perforation location and the location where the sheet first touches the carrier roll, helps to isolate the sheet at the perforations from tension variations, occurring between the drum and the parent reel.
The perforation line is thereafter transported along the periphery of the wrapped carrier roll to the predetermined position in the machine where the cross cutting has to take place, i.e., when seen in the web running direction, to a position behind the closest distance between the peripheries of the first and second carrier rolls. Due to the perforation, the cross cutting means does not need to be more or less sharp (as necessary in the first embodiment), but only be designed to abut against the web near the cross cutting line in a position of the machine which is close to the intended cutting position. According to this embodiment, the location of the perforation line, when arrived in the cross cutting position within the machine, does not need to be identical with the line along which the cross cutting means is clamping the web against the wrapped carrier roll. Instead, the cross cutting line, when arrived in the cross cutting position, may be positioned beyond the clamping line of the cross cutting device when seen in the web running direction. Thereby, a small strip of the arriving web, i.e., at the upstream side of the cross cutting line, extends in cross machine direction between the clamping line of the cross cutting means and the cross cutting line. This strip can be gripped, i.e., clamped easily by a clamping device being moved into the cross cutting position from the opposite side with respect to the movement of the cross cutting means. Such pre-perforation eases the cross-cutting and allows a simple procedure for applying fixing means, like an adhesive, close to both sides of the cross cutting line to the web in order to fix the arriving web edge to a new core for the next winding process and the leaving web edge to the surface of the wound roll.
The aforementioned and claimed procedural steps and components described in the embodiments and to be used in accordance with the invention are not subject to any special exceptions with respect to their procedural conditions, size, design, material selection and technical conception, such that the selection criteria known in the relevant sphere of application can find unlimited use.